At each time step the resulting volumetric field is
\(F_t = F \circ W_{t\rightarrow c}\) .
HyperNeRF [1]} addresses topological change on top of Nerfies by outputting a two-dimensional “ambient” coordinate \(\mathbf {w}\)  encoding the topological change in addition to the canonical point \(\mathbf {x}_c\) ,
\(W_{t\rightarrow c}:(\mathbf {x}, \mathbf {\varphi }_t)\mapsto (\mathbf {x}_c, \mathbf {w}).\) 
